Currently, the number of different wireless access interfaces is increasing rapidly. Most notably, there are an increasing number of WiFi access points available as hotspots or belonging to corporate networks. Since the access to these networks needs to be automated, one of the tasks of the connection manager, which might be a part of an operating system environment, is to decide which of the available access points (or base-stations) should be used. While the invention is described in the context of WiFi (IEEE 802.11), those skilled in the art will appreciate that the same problem addressed herein may be present in connecting to other wireless networks as well.
In connecting to an access point, the end-user (application) is most often interested in achieving the maximum available bit-rate from the access point. Although WiFi access points advertise over their beacons the supported bit-rates, this information is not particularly useful because the beacons are sent over the low bit-rate, robust modulation scheme (1 Mbps) and hence can be heard over the larger distance range. In fact, beacons are received further away than the actual high-speed modulation schemes (e.g. 54 Mbps, 11 Mbps) can work reliably. Also, the final decision on the applicable bit-rate is typically after the connection is established, and decided based on the link-layer error rate. This means that the remote client (STA) must first associate to an access point (AP) and then try the highest possible bit-rate for communication. If the communication fails (e.g., too many un-received ACKs), the system tries the next lowest-level and so forth. This technique naturally increases latency and may actually lead to the initial selection of a sub-optimal access point.
Hence the information provided in beacons is purely informative and does not reflect in any way what the real download bandwidth will be for a wireless station. A simple method for wireless stations is desired whereby the achievable download bandwidth based on signal-to-noise (SNR) or SINR (signal-to-interference-noise) received from the most optimal access point may be statistically estimated. Such a statistical estimation will provide a better idea of the most probable bit-rate that can be achieved after the actual connection is built (and without waiting for the connection to be built).
However, those skilled in the art will appreciate that the value returned by such a technique will represent a best case estimation of the bandwidth, as the value does not take into account the possible collisions resulting from contention of multiple wireless stations at the physical layer. Accordingly, it is further desired to apply a correction factor to the computed bandwidth that is based on the historical memory of previous estimations in order to adjust the estimated bit-rate and thus come closer to a real estimate. The present invention is designed to meet such needs in the art.